Multi-band antenna for portable terminal with radiators on opposite surfaces of substrate

Abstract

A multi-band built-in antenna of a portable terminal is provided. The antenna includes a first antenna radiator on a front surface of a substrate (e.g., a main board), and a second antenna radiator on an opposite surface of the substrate. The substrate has ground surfaces on both sides separated from a non-ground area on which the radiators are disposed. The first radiator may be in the form of a Planar Inverted F Antenna (PIFA), with a first end branched off into two parts, one part used for power feeding and the other part electrically coupled to the ground surface. The first radiator has a portion that extends from the first end to an opposite end. The second radiator is continuous from the opposite end of the first radiator through a via (hole) in the main board.

What is claimed is: 
     
       1. A multiband antenna of a portable terminal, comprising:
 a substrate having a ground area and a non-ground area on each of a front surface and an opposite surface thereof; and an antenna radiator comprising: 
 a first antenna radiator disposed on the non-ground area of the front surface of the substrate, having a first end branched off into two parts on the front surface so that one part is used for power feeding and the other part is electrically connected to the ground area of the front surface, the first antenna radiator having a portion that extends from the first end towards an opposite end; 
 a second antenna radiator disposed on the non-ground area of the opposite surface, and continuous from the opposite end of the first antenna radiator through a via in the substrate; and 
 a third antenna radiator on the opposite surface, driven through coupling from the second antenna radiator, the third antenna radiator aligned with the one part used for power feeding and having one end separated by a specific interval for coupling with an end portion of the second antenna radiator to extend a bandwidth of the multiband antenna; 
 wherein the first and second antenna radiators are arranged to overlap to form a loop structure with respect to one another, the loop structure defining only a single loop forming a central region that is devoid of the first and second antenna radiators on the front and opposite surfaces of the substrate. 
 
     
     
       2. The multiband antenna of  claim 1 , wherein the loop structure is a rectangular loop structure, and the loop structure is configured to improve a high band resonance condition of the second antenna radiator. 
     
     
       3. The multiband antenna of  claim 1 , wherein the third antenna radiator comprises a first portion in a position superposed to a feeding pattern branched off from the first antenna radiator and a second portion superposed to the portion of the first antenna radiator that extends from the first end towards the opposite end by being bent at the first portion. 
     
     
       4. The multiband antenna of  claim 3 , wherein the first antenna radiator has a length of λ/4. 
     
     
       5. The multiband antenna of  claim 4 , wherein the substrate is a main board of the portable terminal, and the antenna radiator is configured with a pattern which has a specific width and a specific length and which is patterned together when the main board is formed. 
     
     
       6. A multiband antenna of a portable terminal, comprising:
 a substrate having a ground area and a non-ground area on each of a front surface and an opposite surface thereof; and an antenna radiator comprising: 
 a first antenna radiator disposed on the non-ground area of the front surface of the substrate, having a first end branched off into two parts on the front surface so that one part is used for power feeding and the other part is electrically connected to the ground area of the front surface, the first antenna radiator having a portion that extends from the first end towards an opposite end; and 
 a second antenna radiator disposed on the non-ground area of the opposite surface, and continuous from the opposite end of the first antenna radiator through a via in the substrate; 
 wherein the first and second antenna radiators are arranged to overlap to form a loop structure with respect to one another, the loop structure forming a central region that is devoid of the first and second antenna radiators on the front and opposite surfaces of the substrate, the opposite end of the first antenna radiator has a section bent from the portion extending in a widthwise direction of the terminal and ending at a location of the via, and the second antenna radiator is in the form of a first section extending from the via in the widthwise direction of the terminal, a central section bent from the first section and extending to a position coinciding with the portion of the first antenna radiator so as to form the closed loop structure, and a third section bent from the central section. 
 
     
     
       7. The multiband antenna of  claim 4 , wherein the substrate is a main board of the terminal and the antenna radiator is a metal plate having a specific pattern attached to the surface of the main board or a flexible printed circuit on which a specific pattern is formed. 
     
     
       8. The multiband antenna of  claim 1 , wherein the first antenna radiator has a length of λ/4. 
     
     
       9. A portable terminal, comprising:
 an antenna including: 
 a substrate having a ground area and a non-ground area on each of a front surface and an opposite surface thereof; and an antenna radiator comprising: 
 a first antenna radiator disposed on the non-ground area of the front surface of the substrate, having a first end branched off into two parts on the front surface so that one part is used for power feeding and the other part is electrically connected to the ground area of the front surface, the first antenna radiator having a portion that extends from the first end towards an opposite end; 
 a second antenna radiator disposed on the non-ground area of the opposite surface, and continuous from the opposite end of the first antenna radiator through a via in the substrate; and 
 a third antenna radiator on the opposite surface, driven through coupling from the second antenna radiator, the third antenna radiator aligned with the one part used for power feeding and having one end separated by a specific interval for coupling with an end portion of the second antenna radiator to extend a bandwidth of the multiband antenna; 
 wherein the first and second antenna radiators are arranged to overlap to form a loop structure with respect to one another, the loop structure defining only a single loop forming a central region that is devoid of the first and second antenna radiators on the front and opposite surfaces of the substrate. 
 
     
     
       10. The terminal of  claim 9 , wherein the loop structure is a rectangular loop structure, and the loop structure is configured to improve a high band resonance condition of the second antenna radiator. 
     
     
       11. The terminal of  claim 9 , wherein the third antenna radiator comprises a first portion in a position superposed to a feeding pattern branched off from the first antenna radiator formed on the front surface of the substrate and a second portion superposed to the portion of the first antenna radiator that extends from the first end to the opposite end by being bent at the first portion. 
     
     
       12. The terminal of  claim 9 , wherein the first antenna radiator has a length of λ/4. 
     
     
       13. The terminal of  claim 12 , wherein the substrate is a main board of the terminal and the antenna radiator is configured with a pattern which has a specific width and a specific length that is patterned together when the main board is formed. 
     
     
       14. The terminal of  claim 12 , wherein the substrate is a main board of the terminal and the antenna radiator is a metal plate having a specific pattern attached to the surface of the main board or a flexible printed circuit on which a specific pattern is formed. 
     
     
       15. The terminal of  claim 9 , wherein the opposite end of the first antenna radiator has a section bent from the portion extending from the first end towards the opposite end, the portion extending in a widthwise direction of the terminal and ending at a location of the via, and the second antenna radiator is in the form of a first section extending from the via in the widthwise direction of the terminal, a central section bent from the first section and extending to a position coinciding with the portion of the first antenna radiator so as to form the loop structure, and a third section bent from the central section.